The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
It is often desirable to determine the torque in a rotatable shaft (rotator) relative to a stationary component (stator). A typical application that includes a rotatable shaft and a stator is an automatic transmission in a motor vehicle. In motor vehicle applications, engine torque models are relied upon to properly adapt engine characteristics to motor vehicle requirements and operator demands.
A preferred method of determining the torque being applied to a rotatable shaft in a transmission includes employing a non-contact torque sensor. Common torque sensors include strain gages, magnetic or optical sensors, magnetoelastic sensors, and surface acoustic wave (SAW) sensors. These torque sensors each measure various parameters such as local strain, angular displacement, or strained-induced change on a magnetic field. Typically these torque sensors have two components. The first component is generally referred to as a transmitter and the second component is generally referred to as a receiver. The receiver is typically coupled to the stator and the transmitter is typically coupled to the rotatable shaft. In the case of magnetoelastic sensors, a current is induced through the receiver and torque applied on the rotatable shaft is transmitted back to the receiver in the form of a magnetic field which is then converted into an estimated torque. One crucial element to determining the amount of torque using these sensors is knowing and controlling the axial alignment of the transmitter relative to the receiver.
Accordingly, one limitation of the above described torque sensors is that a discrepancy in the expected axial alignment of the transmitter relative to the receiver can increase the margin of error in the torque calculation. Tolerance stack and operating end play in automotive transmissions may lead to misalignment of the receiver and the transmitter. Moreover, the system tolerances between the rotatable shaft and the stator are often not precisely known, and therefore the expected axial alignment of the transmitter relative to the receiver will be an estimate. Therefore, there is a need in the art to provide a device that reduces the error between the expected axial alignment of the transmitter relative to the receiver and the actual axial alignment of the transmitter relative to the receiver.